The present invention relates to an apparatus for driving a surfboard and more particularly to a water jet propelling device powered by an internal combustion engine mounted on a rear portion of the surfboard for driving the surfboard.
In recent years, although a surfboard powered by the internal combustion engine has been developed, an indeal water jet propelling device and engine and engine exhaust system have not yet been provided. For example, the engine is mounted on an engine mounting box which has sufficient buoyancy to prevent the submergence of the rear portion of the surfboard by the weight of the engine and the water jet propelling device. In such a disposition, it is preferable to provide the water jet propelling device and the engine exhaust system in the engine mounting box with a device preventing entry of water into the engine from the exhaust system, and further to provide a cooling water system for the engine in which a part of the water jet is used as the cooling water. To meet such requirements, the engine mounting box is complex in construction.